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Objective: To measure the horizontal vergence (BI and BO vergence) used by patients to maintain binocular vision through the use of prisms.
Gradually increasing the prism causes the horizontal retina to shift, forcing the patient to use the vergence system to compensate for this shift.
To measure the gathering and dispersing capabilities of BI and BO, three aspects of data need to be obtained:
(1) Blur point: Indicates that the patient can no longer use the vergence to compensate for the retinal shift caused by the prism, but can still maintain stable accommodation.
(2) Rupture point: Indicates that the patient has exhausted all vergence potential and can no longer maintain binocular vision.
(3) Recovery point: Indicates that the induced retinal detachment gradually decreases, allowing re-applying vergence to obtain binocular single vision.

facility:

① Comprehensive refractometer
② A distance vision chart with a single visual mark

Preparation:

(1) On the comprehensive refractor, adjust the patient's far refractive correction and interpupillary distance.
(2) Displays a single optotype, which is the row above the best corrected visual acuity of the poor eye.
(3) Adjust the Risley prism to the zero position and place it in front of the patient's eyes, and adjust the prism degree in the horizontal position.

step:

(1) Ask the patient to open his eyes and ask him what he sees. The patient should see a clear visual mark. If two optotypes are seen, the examination is concluded and recorded as "diplopia".
(2) Instruct the patient to focus on the visual mark and try to keep it clear, and ask the patient to report when the following situations occur:

① Blurred vision (fuzzy point)
② Visual target becomes two (break point)
③ Optotype moves to the left or right, which means that one eye is suppressed.

Once this phenomenon occurs, the inspection should be stopped, recorded (suppressed) and pointed out which eye; it can be judged which eye is suppressed by asking the moving direction of the optotype; the optotype will move to the direction of the top of the prism in front of the non-inhibited eye.
(3) Simultaneously increase the prism power of both eyes at a rate of about 1△ per second, do BI inspection first and then BO inspection. This is because the BO vergence inspection will affect accommodation and convergence to some extent, and then it is possible Affects the result of BI vergence check.
(4) When the patient reports the aforementioned three points, record the sum of the prism power of both eyes. First, when the patient reported that the visual target became blurred (blurred point), record; secondly, when the patient reported that the visual target became double (ruptured point), it was recorded.
(5) Slightly increase the prism power in the same direction to cross the rupture point, and then decrease the prism in the opposite direction until the patient reports that the visual mark becomes one again, which is the rupture point, and record the sum of the prism powers in front of both eyes at this time.
(6) Similarly, repeat steps 2 to 5 to complete the BO inspection.

Smoking, obesity, excessive eye use, eye injury or inflammation, etc., may increase the incidence of cataracts. In addition to improving unhealthy lifestyles, it is also necessary to have regular eye examinations.

Post time: Mar-18-2023